Mercury and other trace elements in farmed and wild salmon from British Columbia, Canada

The present study reports measured levels of Hg and other trace elements in commercial salmon feed; farmed Atlantic, coho, and chinook salmon (n = 110); and wild coho, chinook, chum, sockeye, and pink salmon (n = 91). Metal concentrations in farmed and wild salmon from British Columbia, Canada, were relatively low and below human health consumption guidelines. Methylmercury in all salmon samples (range, 0.03-0.1 mu g/g wet wt) were below the 0.5 mu g/g guideline set by Health Canada. Negligible differences in metal concentrations were observed between the various species of farmed and wild salmon. Metal concentrations generally were higher in commercial salmon feed compared to farmed salmon. Mercury showed slight bioaccumulation potential in farmed salmon, with biomagnification factors (BMFs) ranging between 0.8 and 1.9. Other metals, such as Cd, Pb, and Ni, exhibited biodilution, with BMFs of much less than one. The relatively low degree of biomagnification of metals observed in farmed salmon likely resulted from the combination of low gastrointestinal absorption efficiency, negligible transfer to muscle tissue relative to other compartments, and a high degree of growth dilution in these fish. Human dietary exposure calculations indicate intakes of Hg, Cd, Pb, Cu, As, and Ni via farmed and wild British Columbia salmon are a relatively small percentage of total intakes (0.05-32%) compared to other Canadian foodstuffs, such as fruits, vegetables, chicken, and beef (68-99%). Although total dietary exposure of Cd, Pb, and Cu approached provisional tolerable daily intake levels, the contribution from British Columbia salmon was less than 2%. Our findings indicate farmed and wild British Columbia salmon remain a safe source of omega-3 highly unsaturated fatty acid intake for cardioprotective and, possibly, other health benefits.